TECHNICAL FIELD
[0001] This disclosure is directed to systems and methods of additive manufacture and, more
particularly, to systems and methods for manufacturing tablets or other items with
substrates that provide controlled release of a chemical using three-dimensional object
printers.
BACKGROUND
[0002] Three-dimensional printing, also known as additive manufacturing, is a process of
making a three-dimensional solid object from a digital model of virtually any shape.
Many three-dimensional printing technologies use an additive process in which an additive
manufacturing device forms successive layers of the part on top of previously deposited
layers. Some of these technologies use inkjet printing, where one or more printheads
eject successive layers of material. Three-dimensional printing is distinguishable
from traditional object-forming techniques, which mostly rely on the removal of material
from a work piece by a subtractive process, such as cutting or drilling.
[0003] Additive manufacturing systems can produce a wide range of items with some proposed
uses including encapsulation of chemicals in soluble substrates for the delivery of
medications or more broadly to chemical delivery devices. The additive manufacturing
system deposits an "active chemical" in the chemical delivery device that is suspended
in an excipient material of a substrate that dissolves in a solvent. As used herein,
the term "active chemical" refers to any chemical that is embedded within a chemical
delivery device for controlled release over time as the chemical delivery device dissolves
in a solvent. As used herein, the term "excipient material" refers to one or more
types of material that form a structure of a chemical delivery device, encapsulate
one or more active chemicals, and control the release of the active chemicals within
the chemical delivery device as the chemical delivery device dissolves in a solvent
or melts in a temperature-controlled chemical release process. In many embodiments,
the excipient materials are substantially non-reactive with the active chemical, but
the excipient materials are soluble in some form of solvent that dissolves the chemical
delivery device to emit the active chemical during use of the chemical delivery device.
Excipient substrate materials are known to the art that dissolve in various solvents
including water, acids, bases, polar and non-polar solvents, or any other suitable
solvent for different applications. Corn starch and microcrystalline cellulose are
two examples of materials that are commonly used as excipient materials for an active
chemical ingredient, although other materials include gelatins, polymers, including
UV-curable polymers, and the like that are used in various chemical delivery devices.
Some forms of excipient material dissolve to deliver the active chemical by melting
or otherwise disintegrating at an operating temperature, such as an elevated melting
temperature that is higher than the typical ambient storage temperature for the chemical
delivery device.
[0004] As the substrate dissolves, the active chemical releases into a medium around the
chemical delivery device and produces a chemical reaction. Applications for such devices
include, but are not limited to, medicament delivery in human and veterinary medicine,
fertilizer and pesticide delivery for agriculture and horticulture, dye release for
tracking the flow of water or other fluids, and delivery of an active chemical in
an industrial process.
[0005] While prior art additive manufacturing systems can produce chemical delivery devices,
some forms of chemical delivery devices require additional structural elements for
proper operation. For example, some time-release chemical delivery devices require
a specific concentration gradient of an active chemical to deliver a dose of the active
chemical that varies over time. In some instances, the tablet does not deliver the
active chemical at a desired rate if the active chemical is distributed within the
volume of the tablet in a non-uniform manner. For example, the rate of release from
the tablet can be too high at some points during the dissolving of the tablet when
it delivers a larger concentration of the active chemical than intended. Also, the
rate of release can be too low when the tablet delivers too low of a concentration
of the active chemical at particular point in time after it is digested. Additionally,
some tablets include two or more types of active chemicals that should not mix while
in the tablet, but should mix once the tablet dissolves. Consequently, improvements
to additive manufacturing processes and systems that enable production of tablets
with precise distributions of active chemicals would be beneficial.
SUMMARY
[0006] In one embodiment, a method of producing a chemical delivery device with a three-dimensional
object printer has been developed. The method includes receiving with a controller
a first concentration parameter for a first active chemical in a first region of a
substrate in the chemical delivery device, generating with the controller halftoned
image data using a stochastic halftone screen and with reference to the first concentration
parameter, the halftoned image data including a plurality of activated pixels that
correspond only to locations of a first portion of a plurality of cavities formed
in a substrate that receive the first active chemical, and ejecting with at least
a first ejector a predetermined amount of a first chemical carrier including the first
active chemical into each cavity in the first portion of the cavities in the substrate
with reference to the halftoned image data to produce the chemical delivery device
with a concentration of the first active chemical corresponding to the first concentration
parameter.
[0007] In another embodiment, a three-dimensional object printer that is configured to produce
a chemical delivery device has been developed. The three-dimensional object printer
includes a support member, at least a first ejector configured to eject a first chemical
carrier including a first active chemical toward the support member, and a controller
operatively connected to the at least first ejector and a memory. The controller is
configured to receive a first concentration parameter for a first active chemical
in a first region of a substrate in a chemical delivery device positioned on the support
member, generate halftoned image data using a stochastic halftone screen stored in
the memory and with reference to the first concentration parameter, the halftoned
image data including a plurality of activated pixels that correspond only to locations
of a first portion of a plurality of cavities formed in a substrate that receive the
first active chemical, and operate the at least first ejector to eject a predetermined
amount of a first chemical carrier including the first active chemical into each cavity
in the first portion of the cavities in the substrate with reference to the halftoned
image data to produce the chemical delivery device with a concentration of the first
active chemical corresponding to the first concentration parameter.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] The foregoing aspects and other features of an additive manufacturing device or printer
that produces chemical delivery devices including at least one active chemical are
explained in the following description, taken in connection with the accompanying
drawings.
FIG. 1 is a diagram of a three-dimensional object printer that is configured to form
chemical delivery devices.
FIG. 2 is a block diagram of a process for forming a chemical delivery device.
FIG. 3A is a plan view of cavities formed in one layer of a chemical delivery device
where each cavity can receive an active chemical.
FIG. 3B is a first cross-sectional view of the chemical delivery device of FIG. 3A.
FIG. 3C is a second cross-sectional view of the chemical delivery device of FIG. 3A.
FIG. 4 is a depiction of concentration graphs for halftoned image data corresponding
to a distribution of an active chemical within a chemical delivery device.
FIG. 5 is a graph depicting a sample of a halftone screen and a corresponding arrangement
of image data for two different active chemicals in a region of a substrate of a chemical
delivery device.
DETAILED DESCRIPTION
[0009] For a general understanding of the environment for the device disclosed herein as
well as the details for the device, reference is made to the drawings. In the drawings,
like reference numerals designate like elements.
[0010] As used herein, the term "halftone screen" refers to a two-dimensional or three-dimensional
arrangement of numeric threshold values that are used to control a distribution of
materials to form a three-dimensional printed object, such as a chemical delivery
device. Each entry in the halftone screen is referred to as a "dot" herein. The dots
are arranged in either a two-dimensional space for a two-dimensional halftone screen
or a three-dimensional space for three-dimensional halftone screen. The term "dot
center" refers to a single dot that serves as a central location for a group of multiple
dots that are each assigned a threshold value based on the value of the dot center.
For example, in some embodiments a controller generates a particular threshold value
at a dot center and "grows" a set of dots with the same threshold value around the
dot center. In other configurations, a dot center corresponding to a cavity that is
a candidate to receive an active chemical is surrounded by "guard" dots that have
a fixed value corresponding to excipient material that encapsulates the cavity. The
dot center corresponds to a location in the halftone screen and the final image data
that optionally receives an active chemical, based on the concentration parameter
of the active chemical and the value of the threshold in the dot center. The surrounding
dots each correspond to locations that receive excipient material and do not receive
an active material to ensure that the active material is encapsulated within the chemical
delivery device.
[0011] As described in more detail below, a printer uses the halftone screens in conjunction
with concentration parameter data for one or more active chemicals to generate "halftoned
image data" or more simply "image data". The image data include two-dimensional or
three-dimensional arrangements of locations that specify a type of material in the
chemical delivery device with each location in the image data being referred to as
a "pixel" herein. Each pixel in the image data corresponds to the location of one
dot in a halftone screen. However, instead of the threshold values in the dots of
the halftone screens, the pixels in the image data each include a value that specifies
one type of excipient material or active material that the printer emits to form a
chemical delivery device with concentration levels of the active chemical that correspond
to the concentration parameters. The term pixel as used herein also includes the ordinary
meaning of the term "voxel" (volumetric-pixel) that refers to the three-dimensional
volumetric units that form the shape and structure of a model for a three-dimensional
printed object. A three-dimensional object printer uses the image data to control
the operation of ejectors or other material dispensers to form the structure and distribute
the active chemicals in a chemical delivery device.
[0012] As used herein, the term "stochastic halftone screen" refers to a halftone screen
in which dot centers are uniformly sized and pseudo-randomly distributed throughout
a two or three dimensional space. Traditional, fixed frequency halftone screens establish
a set of dot centers at fixed points, usually based on a crystalline lattice. Common
halftone screens might place dot centers at the vertices of a square or hexagonal
lattice in two dimensions (or at the vertices of cubes, or the centers of close-packed
spheres in three dimensions). A fixed frequency halftone screen increases the number
of dots which are "on" by adding additional dots next to an existing dot center. Stochastic
screens increase the number of dots that correspond to a particular threshold value
or range of threshold values by adding additional dot centers, which are generally
not adjacent to a previous dot center.
[0013] As used herein, the term "vector halftone screen" refers to a type of halftone screen
where a single halftone screen positions multiple types of active chemicals in different
locations to prevent mixing of different active chemicals during the manufacturing
process of a chemical delivery device. The vector halftone screen differs from many
prior art halftone screens that are associated with printed images where each color
in a multi-color printer (e.g. a cyan, magenta, yellow, black) printer has a separate
halftone screen and the printer generates a separate set of image data for each color,
which is often referred to as a "color separation". In conventional printing, many
printed images include halftoned image data in multiple color separations that print
two colors of ink to the same physical location on a sheet of paper as part of a printed
image, which is sometimes desirable when printing color images. However, in many chemical
delivery device embodiments, different active chemicals, which are analogous to different
colors of ink, should not be printed in a single physical location since the active
chemicals should only mix upon being released from the chemical delivery device. By
contrast, the vector halftone screens enable forming chemical delivery devices that
employ multiple active chemicals, using a single halftone screen that prevents multiple
active chemicals from being printed to a single location.
[0014] Using the vector halftone screen, a controller assigns different threshold ranges
to different active chemicals based on the concentration parameter value of each active
chemical. The threshold ranges do not overlap so that each dot center within the vector
halftone can be assigned to at most one type of active chemical or to an excipient
material for dots that do not correspond to any active chemical. At each dot location
in the halftone screen, a controller identifies the threshold value in the halftone
screen and generates a pixel of image data that corresponds to at most one active
chemical based on "stacked" threshold levels for one or more active chemicals. For
halftone dots with threshold values that do not correspond to the ranges for any active
chemicals, the controller generates an image data pixel corresponding to an excipient
material that fills the pixel.
[0015] As is described in more detail below in conjunction with FIG. 5, one practical embodiment
of the halftone screen includes dots with an 8-bit numeric range of threshold values
(0 - 255). A controller receives concentration parameters, optionally as a percentage
value, and assigns non-overlapping or "stacked" portions of the 8-bit numeric range
to each concentration parameter based on the size of the concentration parameters
(e.g. 25% for Chemical A → 0 - 63; 16% for Chemical B → 64 - 104; and Excipient material
for the remaining values 105 → 255). The controller uses the dot values of the vector
halftone screens at different locations to determine which compound is printed for
each corresponding pixel in the image data by assigning each dot to one chemical based
on the value of the dot and the numeric ranges of each chemical (e.g. a dot value
of 24 → image data pixel for Chemical A; a dot value of 134 → image data pixel for
Excipient material). The statistical distribution of threshold values within the vector
halftone screen ensures that multiple chemicals are distributed evenly within each
region of the chemical delivery device. Thus, the vector halftone screen and corresponding
halftone process enables generation of image data that correspond to a distribution
of one or more active chemicals that prevents mixing of the active chemicals during
the process of producing the chemical delivery device.
[0016] The terms "stochastic halftone screen" and "vector halftone screen" as used herein
do not refer to mutually exclusive properties of halftone screens. Instead, a single
halftone screen can have both the stochastic and vector properties described above
that form a stochastic vector halftone screen. For example, in a chemical delivery
device that only uses a single active chemical, a stochastic halftone screen enables
production of the chemical delivery device with a distribution of the single active
chemical in different regions of the chemical delivery device based on concentration
parameters for the single active chemical in each of the regions. While the halftone
screen in the single chemical configuration is optionally a vector halftone screen,
the vector property is not required since there is only a single active chemical.
In production of chemical delivery devices that include two or more active chemicals,
the printer utilizes a halftone process with the stochastic vector halftone screen
to control the distribution of two or more active chemicals within the chemical delivery
device.
[0017] As used herein, the term "process direction" refers to a direction of movement of
a support member past one or more printheads during a three-dimensional object formation
process. The support member holds the three-dimensional object during the print process.
In some embodiments, the support member is a planar member such as a metal plate,
while in other embodiments the support member is a rotating cylindrical member or
a member with another shape that supports the formation of an object during the three-dimensional
object printing process. In some embodiments, the printheads remain stationary while
the support member and object moves past the printhead. In other embodiments, the
printheads move while the support member remains stationary. In still other embodiments,
both the printheads and the support member move.
[0018] As used herein, the term "cross-process direction" refers to a direction that is
perpendicular to the process direction and in the plane of the support member. The
ejectors in two or more printheads are registered in the cross-process direction to
enable an array of printheads to form printed patterns of an excipient material or
active chemical material over a two-dimensional planar region. During a three-dimensional
object printing process, the printheads eject drops of the excipient material to form
successive layers of structure and cavities within a chemical delivery device.
[0019] As used herein, the term "z-axis" refers to an axis that is perpendicular to the
process direction, the cross-process direction, and to the plane of the support member
in a three-dimensional object printer. At the beginning of the three-dimensional object
printing process, a separation along the z-axis refers to a distance of separation
between the support member and the printheads that form the layers of excipient material
in a three-dimensional printed chemical delivery device. As the ejectors in the printheads
form each layer of excipient material, the printer adjusts the z-axis separation between
the printheads and the uppermost layer to maintain a substantially constant distance
between the printheads and the uppermost layer of the object during the printing operation.
In some embodiments, the support member moves away from the printheads during the
printing operation to maintain the z-axis separation, while in other embodiments the
printheads move away from the partially printed object and support member to maintain
the z-axis separation.
[0020] FIG. 1 depicts an additive manufacturing device embodied as a three-dimensional object
printer 100, or more simply printer 100. The printer 100 is configured to operate
printheads to form a three-dimensional printed chemical delivery device 300 that includes
one or more active chemicals encapsulated within a structure formed from at least
one type of excipient material. The printer 100 includes a support member 102, printhead
arrays 104A - 104C, 108A - 108C, and 112A - 112C, an ultraviolet (UV) curing device
116, controller 128, memory 132, and a leveler 118. In the illustrative embodiment
of FIG. 1, the three-dimensional object printer 100 is depicted during formation of
a three-dimensional chemical delivery device 300 that is formed from a plurality of
layers of excipient material. The chemical device 300 includes multiple layers of
cavities that receive active chemicals in the form of drops of chemical carriers that
one or more ejectors in the printhead arrays 104A - 104C and 108A - 108C eject into
portions of the cavities with reference to concentration parameters in different regions
of the chemical delivery device 300.
[0021] In the embodiment of FIG. 1, the support member 102 is a planar member, such as a
metal plate, that moves in a process direction P. The printhead arrays 104A - 104C,
108A - 108C, and 112A - 112C, UV curing device 116, and leveler 118 form a print zone
110. The member 102 carries any previously formed layers of excipient material along
with cavities that have been filled with an active chemical material through the print
zone 110 in the process direction P. During the printing operation, the support member
102 moves in a predetermined process direction path that passes the printheads multiple
times to form successive layers of the excipient material and active chemicals in
the chemical delivery device 300. In some embodiments, multiple members similar to
the member 102 pass the print zone 110 in a carousel or similar configuration. One
or more actuators move the member 102 through the print zone 110 in the process direction
P. In the embodiment of FIG. 1, an actuator also moves the support member 102 in the
direction Z away from the components in the print zone 110 after each layer of excipient
material is applied to the support member 102 to form the chemical delivery device
300. The actuator moves the support member 102 in the Z direction to maintain a uniform
separation between the uppermost layer of the chemical delivery device 300 and the
components in the print zone 110.
[0022] Each of the printheads in the printhead arrays 104A - 104C, 108A - 108C, and 112A
- 112C includes at least one ejector. In the illustrative printhead embodiments of
FIG. 1, each printhead includes a two-dimensional array of ejectors that eject drops
of liquid using, for example, piezoelectric or thermal transducers. In many practical
embodiments, each printhead includes an ejector array with a density that enables
printing of several hundred or thousand drops of material per linear inch (DPI). The
printer 100 depicted in FIG. 1 ejects drops of two different types of active chemical
with the printhead array 104A - 104C being configured to eject drops of a first active
chemical and the printhead array 108A - 108C being configured to eject drops of the
second active chemical. The printhead array 112A - 112C ejects drops of an excipient
material, such as a polymer material, which forms the structure of the chemical delivery
device 300, including the cavities within the chemical delivery device 300 that receive
active chemicals.
[0023] In many embodiments, the active chemical is dissolved or suspended in a chemical
carrier for ejection as liquid drops through the inkjets in the printheads 104A -
104C and 108A - 108C. In some configurations, the chemical carrier evaporates within
the cavities of the chemical delivery device 300 prior to sealing each cavity to leave
the active chemical in the cavity, while in other embodiments the chemical carrier
remains in a liquid state within the cavity. While the precise formulation of the
chemical carrier can vary for different types of chemical delivery devices, the chemical
carrier is generally a liquid form of an excipient material. That is to say, the chemical
carrier does not interact with the active chemicals or substantially change the nature
of the chemical reaction as the chemical delivery device dissolves and emits the active
chemicals. Of course, some active chemicals are already available in a liquid form
that is compatible with the printheads and ejectors in the printer 100. In these configurations,
the chemical carrier and the active chemical are the same material.
[0024] While each of the printhead arrays 104A - 104C, 108A - 108C, and 112A - 112C is depicted
as including three printheads, alternative configurations can include fewer printheads
or a greater number of printheads to accommodate print zones with different sizes
in the cross-process direction. Alternative embodiments of the printer 100 include
a greater or lesser number of printhead arrays to handle different combinations of
active chemicals. While the printhead arrays 104A - 104C, 108A - 108C, and 112A -
112C remain stationary during operation in the printer 100, alternative printer embodiments
include one or more printheads that move in the cross-process direction
CP, process direction
P, or in both the cross-process and process directions. The moving printheads form
the structure of a three-dimensional chemical delivery device and deposit active chemicals
within the chemical delivery device. Additionally, while FIG. 1 depicts a single chemical
delivery device 300 for illustrative purposes, in many practical embodiments the printer
100 forms multiple chemical delivery devices simultaneously, such as a sheet of the
excipient material containing multiple tablets that can be swallowed by an average
human, using the printhead arrays depicted in FIG. 1. The larger excipient material
sheet is then mechanically separated into individual chemical delivery devices after
completion of the operation of the printer 100.
[0025] In the embodiment of the printer 100 shown in FIG. 1, the printheads 112A - 112C
act as a dispenser for the excipient material. In an alternative configuration to
the print zone 110, an excipient powder dispenser includes a spreader (not shown)
that emits the excipient material as a thin layer of powder that covers the upper
surface of the chemical delivery device 300. The powder dispenser is positioned across
the print zone 110 in a similar configuration to the UV curing device 116. The ejectors
in the printheads 112A - 112C eject drops of a liquid binder material onto selected
locations of each powder layer to bind and harden the powder into a durable portion
of the chemical delivery device. The UV curing device 116 optionally cures the binder
in some embodiments. The excess powder that does not receive the binder is removed
from the chemical delivery device 300 to expose cavities that receive the chemical
carrier that includes the active chemicals from the printhead arrays 104A - 104C and
108A - 108C.
[0026] In the printer 100, the UV curing device 116 is an ultraviolet light source that
produces UV light across the print zone 110 in the cross-process direction
CP. The UV light from the UV curing device 116 hardens the excipient material on the
uppermost layer of chemical delivery device 300 to form a durable portion of the chemical
delivery device 300. The UV curing process solidifies the excipient material to accept
additional layers of excipient material and to form arrays of cavities that can contain
a liquid chemical carrier with an active chemical as ejected from the ejectors in
one or more printhead arrays, such as the arrays 104A - 104C and 108A - 108C.
[0027] As use herein, the term "leveler" refers to a member that is configured to engage
the uppermost surface of each layer of the excipient material in a chemical delivery
device before the UV curing device 116 cures the excipient material. In the printer
100, the leveler 118, which is also referred to as a planarizer, applies pressure
and optionally heat to smooth the uppermost layer of excipient material in the chemical
delivery device 300 and form a uniform surface that receives an additional layer of
the excipient material during a subsequent pass through the print zone 110. In some
embodiments, the leveler 118 is a roller coated with a low surface energy material
to prevent adhesion of the excipient material in the chemical delivery device 300
to the surface of the leveler 118. While the other components in the print zone 110
remain at a predetermined distance in the
Z direction from the chemical delivery device 300, the leveler 118 engages the chemical
delivery device 300 during at least some passes through the print zone 110 to smooth
the uppermost layer of excipient material.
[0028] The controller 128 is a digital logic device such as a microprocessor, microcontroller,
field programmable gate array (FPGA), application specific integrated circuit (ASIC)
or any other digital logic that is configured to operate the printer 100. In the printer
100, the controller 128 is operatively connected to one or more actuators that control
the movement of the support member 102, the printhead arrays including the printhead
arrays 104A - 104C, 108A - 108C, and 112A - 112C, the UV curing device 116, and the
leveler 118. The controller 128 is also operatively connected to a memory 132. In
the embodiment of the printer 100, the memory 132 includes volatile data storage devices
such as random access memory (RAM) devices and nonvolatile data storage devices such
as solid-state data storage devices, magnetic disks, optical disks, or any other suitable
data storage devices. The memory 132 stores programmed instructions 136 for the operation
of the controller 128 to operate components in the printer 100. The memory 132 also
stores chemical delivery device structure data 138 that include a three-dimensional
(3D) representation of the shape and structure of one or more types of chemical delivery
devices including specific arrangements of cavities within the chemical delivery devices.
The chemical delivery device structural data 138 include, for example, a plurality
of two-dimensional image data patterns that correspond to each layer of excipient
material that the printer 100 forms to produce the chemical delivery device 300. The
memory 132 also stores concentration parameters 140 that specify the concentration
levels of at least one active chemical within one or more regions of the chemical
delivery device 300. The memory 132 also stores one or more stochastic or vector halftone
screens 142. As described in more detail below, the stochastic or vector halftone
screens enable the printer 100 to control the distribution of active chemicals to
different portions of the cavities formed in the chemical delivery device 300. The
controller 128 executes the stored program instructions 136 to operate the components
in the printer 100 to form the three-dimensional structure of the excipient material
in the chemical delivery device 300. The controller 128 also executes the stored program
instructions to generate halftoned image data and control ejection of drops of the
active chemicals into portions of the cavities formed in the chemical delivery device
300 based on the concentration parameter data 140 and halftone screens 142 for different
regions of the chemical delivery device 300.
[0029] FIG. 2 depicts a process 200 for forming a chemical delivery device with a range
of concentration levels for one or more active chemicals in a substrate formed with
one or more forms of excipient material. In the discussion below, a reference to the
process 200 performing an action or function refers to the operation of a controller
in an additive manufacturing device, such as a three-dimensional object printer, to
execute stored program instructions to perform the function or action in association
with components in the additive manufacturing device. The process 200 is described
in conjunction with the three-dimensional object printer of FIG. 1 for illustrative
purposes.
[0030] During process 200, the printer 100 optionally forms a substrate layer in the chemical
delivery device from an excipient material with a plurality of exposed cavities that
are available to receive an active chemical from the printer 100 during the process
200 (block 204). In one embodiment, the printer 100 forms the substrate from a powdered
excipient material using a spreader that supplements the printheads 112A - 112C. The
controller 128 operates ejectors in one group of the printheads, such as the printheads
112A - 112C, to eject a binder material in a predetermined pattern to form a hardened
layer of the excipient material. The controller 128 operates the ejectors in the printheads
112A - 112C based on the chemical delivery device structure data 138 to form each
layer of the chemical delivery device 300 with a predetermined structure and arrangement
of cavities. The controller 128 also forms cavities in the substrate in locations
that do not receive the binder material where excess powder that does not receive
the binder is removed after the printer 100 forms a layer of cavities. The printer
100 generally forms each set of cavities from a plurality of layers of the excipient
material that form the floor and lateral walls of each cavity.
[0031] In another embodiment, one or more printhead arrays in the printer 100 eject drops
of the excipient material that harden to form the substrate and the cavities from
multiple layers of the excipient material using, for example, a UV curable polymer
or other suitable excipient material. The controller 128 uses the chemical delivery
device structure data 138 to control the ejection of drops of the excipient material
from the printheads 112A - 112C to form layers of the chemical delivery device with
the predetermined shape and arrangement of cavities. In still another embodiment,
a device other than the printer 100 forms the substrate and the cavities. The printer
100 receives the substrate with exposed cavities on the support member 102.
[0032] FIG. 3A - FIG. 3C depict an example of a chemical delivery device 300 with multiple
layers of cavities. FIG. 3A depicts a plan view of the substrate in the chemical delivery
device 300 with an array of cavities, such as cavity 324, formed in one layer of the
chemical delivery device 300. In the example of FIG. 3 the printer 100 is configured
to generate halftoned image data for an active chemical that is ejected into a portion
of the cavities that are shown in FIG. 3A. In the illustrative embodiment of FIG.
3A, the printer 100 receives different concentration parameters for three different
regions 304, 308, and 312 in the exposed layer. While FIG. 3A depicts the regions
304 - 312 in one layer of the chemical delivery device 300, in many embodiments the
regions extend through the cavities that are formed in multiple layers of the chemical
delivery device 300 to form three-dimensional regions. Furthermore, while FIG. 3A
depicts three regions 304 - 312 for illustrative purposes, alternative configurations
can include a different number of regions and further include a gradient of varying
concentration parameters throughout the chemical delivery device 300.
[0033] FIG. 3B and FIG. 3C depict cross-sectional views of a portion of the chemical delivery
device 300 taken along line 340. FIG. 3B depicts one layer of exposed cavities including
the cavity 324 where the exposed cavities are approximately hemispherical in shape
to receive drops of a liquid chemical carrier and the active chemical. The chemical
delivery device includes multiple layers of cavities in a three-dimensional arrangement
including the cavity 332. FIG. 3C depicts another configuration in which the excipient
material that forms the upper layer, including the cavity 324, by almost completely
forming it with an opening at the top of each exposed cavity that is large enough
to enable the chemical carrier and active chemical to enter the cavities and to substantially
fill the cavities. The excipient material in the chemical delivery device 300 seals
the lower layers of cavities. In some embodiments, the printer 100 moves the support
member 102 and chemical delivery device 300 through the print zone 110 multiple times
to form the structure of the chemical delivery device 300 from the excipient material
that provides a structure with multiple layers of cavities. The printer 100 ejects
drops of the active chemical to fill a selected portion of the exposed cavities in
each layer of the chemical delivery device 300. The operation of the printer 100 to
generate halftoned image data for different regions of the chemical delivery device
300 and eject a chemical carrier including one or more active chemicals into different
sets of cavities using a stochastic halftone screen or a vector halftone screen is
presented in further detail below.
[0034] The excipient material that forms the structure of the chemical delivery device 300
isolates each of the cavities from each other to prevent fluid communication between
cavities. In particular, the excipient material prevents the formation of fluid channels
between cavities that could enable a larger than expected release of active chemical
when the excipient material dissolves to expose fluidly coupled cavities. Additionally,
in chemical delivery devices that include two or more active chemicals, the isolated
cavities prevent the active chemicals from combining prior to the dissolution of the
excipient material in the chemical delivery device 300. While FIG. 3B and FIG. 3C
depict spherical cavities, the chemical delivery device 300 can include cavities with
different sizes and shapes, including oblate spheroids and cylindrical cavities for
different types of chemical delivery devices.
[0035] As depicted in FIG. 3A, the chemical delivery device 300 includes multiple regions
304 - 312, and the printer 100 processes concentration parameter data in multiple
regions of the substrate to generate halftoned image data that enable delivery of
different densities of the active chemicals to the cavities within each region. For
example, in one chemical delivery device configuration, the concentration parameters
increase from the outermost region 304 through the intermediate region 308 to the
innermost region 312. Since the volume of each of the regions decreases from the exterior
region 304 to the center region 312, a proper selection of concentration levels enables
the chemical delivery device 300 to emit the active chemical at a substantially constant
rate as the chemical delivery device 300 dissolves. Of course, in alternative configurations
the concentration parameters can affect the rate of emission for the active chemical
in a wide variety of ways including a gradient that enables the chemical delivery
device 300 to emit one or more active chemicals at varying rates over time as the
chemical delivery device 300 dissolves.
[0036] While the chemical delivery device 300 is formed with a cylindrical center with two
hemispheres at each end of the cylinder in a shape that is often associated with medication
tablets and other chemical tablets, the printer 100 is configured to form the substrate
with a wide variety of shapes and sizes of the chemical delivery device and individual
cavities. The chemical delivery device 300 is merely an illustrative embodiment of
a three-dimensional device with a plurality of layers having cavities to receive various
concentrations of an active chemical.
[0037] Referring again to FIG. 2, the process 200 continues as the printer 100 receives
concentration parameter data that specify the concentrations levels for one or more
active chemicals in one or more regions of the chemical delivery device (block 208).
The concentration parameters include a numeric value that specifies a proportion of
the cavities in a given region of the chemical delivery device that receive the corresponding
active chemical. In the printer 100, the controller 128 receives stored concentration
parameter data 140 from the memory 132. The concentration parameters correspond to
one or more active chemicals within at least one region of the chemical delivery device
300. In one embodiment, a concentration parameter for each active chemical is specified
as a percentage in a range of 0% to 100% where 0% indicates that the active chemical
is absent from a particular region of the chemical delivery device, 100% indicates
that all available cavities in the region should receive the active chemical, and
an intermediate percentage that corresponds to a specific number of cavities in the
region that receive the chemical in the region. Some chemical delivery devices include
regions with concentration parameters for two or more active chemicals. The sum of
the concentration parameters does not exceed 100% or some other predetermined maximum
parameter value to ensure that the substrate has sufficient cavity locations for all
of the active chemicals in the region of the chemical delivery device.
[0038] FIG. 4 depicts a graph 400 of concentration parameters for two different active chemicals
(Chemical A and Chemical B) in different regions of a chemical delivery device. In
FIG. 4 a total of forty regions in a three-dimensional cylindrical volume approximates
the shape of a chemical delivery device, such as the device 300 of FIG. 3. Each region
corresponds to a three-dimensional concentric shell starting from a region that surrounds
the center of the cylinder (x-index 1) and extending to the exterior of the cylinder
(x-index 40). The example of FIG. 4 depicts concentration gradients for the two different
active chemicals. As used herein, the term "concentration gradient" refers to a change
in the concentration levels of the active chemical distributed through the different
regions of the chemical delivery device that the printer 100 produces based on a plurality
of concentration parameters for multiple regions in the chemical delivery device.
The different concentration gradients enable different configurations of the chemical
delivery device to emit the active chemicals at substantially constant rates, increasing
or decreasing rates, or even oscillating rates as the chemical device dissolves.
[0039] In the example of FIG. 4, the concentration gradient for the first active chemical
A specifies a decreasing concentration from the center of the chemical delivery device
outwards towards the exterior of the device, while the concentration gradient for
the second active chemical B specifies an increasing concentration gradient from the
center of the chemical delivery device outwards towards the exterior of the device.
Alternative concentration gradients include a plurality of concentration parameters
that form non-linear and non-monotonic changes in the concentration through different
regions of the chemical delivery device. While FIG. 4 depicts concentration gradients
over three-dimensional regions in a chemical delivery device with an approximately
cylindrical shape, similar concentration gradients are also applicable to chemical
delivery devices with a wide range of shapes. Another approximation of the chemical
delivery device 300 of FIG. 3A models the volume of the chemical delivery as a cylinder
with two spheres:
V = (4
πr2 + 2
πrh)
δr. Similar approximations for the three-dimensional geometry of various chemical delivery
devices are known to those of ordinary skill in the art.
[0040] Referring again to FIG. 2, the process 200 continues as the controller 128 in the
printer 100 generates halftoned image data using a stochastic halftone screen, (which
may also be a vector halftone screen if multiple compounds are being printed) with
reference to the one or more concentration parameters in each region of the image
data corresponding to the substrate (block 212). The controller 128 generates pixels
of image data using the threshold values of corresponding dots in the halftone screens
and the threshold ranges of the active chemicals and excipient materials based on
the concentration parameters for one or more active chemicals. As used herein, the
term "activated pixel" refers to a pixel location in the halftoned image data that
receives an active chemical, while the remaining pixels that form the structure of
the chemical delivery device receive an inactive or excipient material. In embodiments
of the process 200 that form chemical delivery devices with two or more active chemicals,
the controller 128 uses the vector halftone screen to generate image data with only
one active chemical in any given pixel location of the image data. The printer 100
also ejects drops of excipient material for the remaining pixels that are not activated
pixels as is described in more detail below. The halftoned image data include a plurality
of activated pixels that correspond only to locations of a portion of a plurality
of cavities formed in a substrate that receive an active chemical. In some configurations,
a region receives one active chemical while in other configurations a single region
receives two or more active chemicals. As described above, the stochastic vector halftone
screen includes an arrangement of dots with threshold values that produces halftoned
image data with a distribution of pixels that corresponds to the physical arrangement
of cavities in the chemical delivery device.
[0041] The halftone process generates the halftoned image data with a predetermined arrangement
of pixels that corresponds to the locations of cavities that are exposed in the substrate
of the chemical delivery device. If the chemicals being dispensed do not have the
same dissolution rate as the excipient material in the target solvent, or if multiple
chemicals are included which must not touch, then the halftone screen also includes
"guard" dots with a predetermined threshold value or range of values that surround
the dots corresponding to different cavities in the chemical delivery device. The
guard dots have a fixed value that never corresponds to an active chemical. The printer
100 generates the halftoned image data based on the guard dots that includes corresponding
"guard" pixels that surround the locations of the cavities and that correspond to
the locations of walls and other structures in the substrate that do not receive drops
of the active chemicals. In FIG 5 the halftone screen includes an arrangement of guard
dots that correspond to the arrangements of cavities in one layer of the chemical
delivery device 300. The guard dots are assigned a predetermined value or range of
values (e.g., 255 in the example of FIG. 5) which ensures that they are only used
for printing the excipient material, and not any of the active chemicals.
[0042] To produce the halftone screens, the controller 128 either uses the predetermined
halftone screen data that are stored in the halftone screen data 142 of the memory
132, or the controller 128 generates pseudo-random numeric threshold values for each
dot that corresponds to a cavity and that is a candidate to receive an active chemical.
Except for situations where a region of the chemical delivery device is saturated
to 100% concentration, only a portion of the cavities in each region receives an active
chemical. The remaining cavities remain empty or the printer 100 fills the empty cavities
with either the excipient material that forms the chemical delivery device 300 or
an inactive material, such as water, glycerin, triglycerides, or another liquid. The
fill material depends upon the chemical properties of the environment in which the
chemical device dissolves. In some embodiments, the chemical carrier that holds the
active chemicals in solution also serves as an inactive liquid when ejectors in the
printer eject the chemical carrier without any dissolved active chemical. The controller
128 uses a thresholding process described below to identify the portions of the pixels
that receive different active chemicals based on the halftone screen dot values and
the threshold ranges.
[0043] FIG. 5 depicts a two-dimensional halftone screen 500 corresponding to a single layer
of one region of a chemical delivery device that the printer 100 uses during the process
200. The halftone screen 500 is an illustrative example of a stochastic vector halftone
screen that is suitable for use in production of a chemical delivery device that incorporates
one or more active chemicals. In the printer 100 the memory 132 stores the halftone
screen 500 and optionally additional two-dimensional or three-dimensional halftone
screens with the halftone screen data 142. FIG. 5 also depicts a table 550 showing
the concentration parameters for two different active chemicals that are distributed
in the halftoned image data. The halftoned screen data 500 are encoded in an 8-bit
numeric range where each dot takes on a value of 0 to 255, although other embodiments
use different ranges and the guard dots could be assigned a different value, such
as 0, in an alternative configuration. In FIG. 5, the dots with values 255 are each
guard dots that correspond to locations of walls or features other than cavities in
the substrate of the chemical delivery device, and the printer 100 does not eject
drops of active chemicals into the locations corresponding to guard dots. FIG. 5 depicts
a single set of guard dots around each potential location for the active chemicals,
but alternative embodiments use a different number of guard dots based on the sizes
and arrangements of the cavities in the substrate. Some embodiments omit guard dots
if separation of the active chemical locations is not required for a particular chemical
delivery device. Additionally, while the halftone screen 500 depicts a single dot
for each cavity, different halftone screen embodiments include dot arrangements for
different sizes and shapes of cavities.
[0044] While FIG. 5 depicts the two-dimensional halftone screen 500 that corresponds to
a region of a single layer of a larger three-dimensional chemical delivery device,
in the printer 100 the halftone screen data 142 typically includes three-dimensional
halftone screens that include multiple layers to define a three-dimensional region
of the chemical delivery device over multiple layers. Some layers of the halftone
screen may include only guard dots that correspond to the excipient material to enable
the printer 100 to form protective layers of the excipient material over previously
filled cavities in the chemical delivery device. In a three-dimensional halftone screen
embodiment, the halftone screen 500 represents one layer in the multi-layer halftone
screen. During operation, the printer 100 forms each layer of the chemical delivery
device using one selected two-dimensional halftone screen portion of a larger three-dimensional
halftone screen for each layer.
[0045] In one embodiment, the halftone screen is stored in the memory 132 prior to the printing
process. As described below, the printer tiles a single halftone screen in a repetitive
process to cover the three-dimensional region occupied by the chemical delivery device
for a wide range of chemical device shapes and sizes to enable a comparatively small
halftone screen to be used to form the image data in one or more regions of a larger
chemical delivery device. The controller 128 adjusts the threshold ranges that receive
active chemicals based on the concentration parameter data to enable the printer 100
to use a single halftone screen to produce image data and printed chemical delivery
devices with different chemical concentration gradients for one or more active chemicals
in different regions of the chemical delivery device. In another embodiment, the controller
128 generates the halftone screen threshold values during the printing process. The
controller 128 generates the numeric values in the dot centers of the screen in a
pseudo-random manner to produce a more uniform distribution than would be achieved
using completely random numbers. For example using a pseudo-random process the controller
128 generates threshold values for the dots where the probability of adjacent cavities
having similar halftone levels, which increases the likelihood that adjacent cavities
receive the same active chemical, is less than would be expected from a purely random
process. In embodiments that use guard dots, the controller 128 only uses the pseudo-random
process to produce the threshold values for the dot centers that align with cavities
in the chemical delivery device and the guard dots (e.g. dot values of 255 in FIG.
5) remain with fixed values.
[0046] During the process 200, the controller 128 generates activated pixels for one or
more active chemicals in the portions of the halftoned image data based on the concentration
parameters for each active chemical within a region and based on the threshold values
in the halftone screen that are assigned to the dot locations for each cavity within
the region. As depicted in the table 550 the concentration parameter for a first active
chemical (Chemical A) is 32%, and the controller 128 generates a threshold range of
0 - 81 (e.g. approximately 32% of 256 available values) using the predetermined scale
of 0 - 255 of FIG. 5. Thus, the controller generates activated pixels in halftoned
image data that are assigned to the first active chemical corresponding to the locations
of dots in the halftoned screen 500 that have a numeric value of 0 - 81. Table 550
includes another concentration parameter of 23% for the second active chemical (Chemical
B) and the controller 128 generates a second numeric range of 82 - 140 (e.g. approximately
23% of the 256 values with an offset of +82 to avoid overlap with the threshold range
of the first chemical) for the second active chemical. The numeric ranges for the
first active chemical and the second active chemical are "stacked" meaning that the
numeric ranges do not overlap to ensure that the controller 128 selects at most one
active chemical for any of the candidate dots in the halftone screen (e.g., dots that
do not have the guard value 255) in the image data 500. The remaining dots that correspond
to the cavities in the substrate with numeric dot threshold values of 141 to 255 do
not receive either of the first or second active chemicals and the controller 128
classifies these pixels as "inactive" in FIG. 5, which indicates that the excipient
material or another inactive material should fill cavities that do not receive the
active chemicals.
[0047] For example, the halftone screen data 500 contains a dot 504 with numeric threshold
value 22. The controller 128 generates an activated pixel for the first active chemical
in the halftoned image data based on the threshold value and the threshold range for
the first active chemical based on the concentration parameter. Similarly, the controller
128 generates an activated pixel for the second active chemical corresponding to the
dot 508, which has the numeric threshold value 101. The controller 128 does not generate
an activated pixel corresponding to the dot 512 with numeric value 175 since the dot
512 does not fall within the threshold of either active chemical. Instead, the controller
128 generates a pixel that is assigned to the excipient material or another inactive
material to fill the cavity that does not receive an active chemical. Similarly, the
controller generates image data pixels corresponding to the excipient material for
all of the guard dots with the value 255.
[0048] In a multi-layer chemical delivery device, the printer 100 optionally generates or
uses a pre-defined three-dimensional halftone screen corresponding to the three-dimensional
arrangements of cavities in multiple layers of the chemical delivery device. The three-dimensional
halftone screen includes dot locations that are candidates to receive active material
and guard dots in a similar configuration to the two-dimensional arrangement of dots
shown in FIG. 5. Three-dimensional halftone screens include multiple planes of dots
similar to the planar screen 500 of FIG. 5 that correspond to different layers of
cavities in the chemical delivery device. If the three-dimensional halftone screen
is smaller than the object to be printed, the controller 128 tiles multiple copies
of the halftone screen, using a space-filling tiling process to produce a larger screen
that completely encompasses the three-dimensional volume of the chemical delivery
device. During operation, the printer 100 ejects drops of the active chemical or chemicals
for an individual layer with a two-dimensional arrangement of cavities with openings
that are exposed to the printheads, such as printheads 104A - 104C and 108A - 108C
in the printer 100. Thus, while the printer 100 generates three-dimensional halftoned
image data in some embodiments, the printer 100 ejects the active materials into individual
layers of cavities in the chemical delivery device that are each arranged in a two-dimensional
layer.
[0049] In an alternative embodiment, the controller 128 further divides the regions in the
three-dimensional chemical delivery device into a series of two-dimensional regions
corresponding to each layer of cavities formed in the chemical delivery device. The
controller 128 generates or loads from memory, 132, the halftone screen as a two-dimensional
arrangement of dots for each layer of cavities in the chemical delivery device based
on the concentration parameters and gradients through the two-dimensional layer. Either
embodiment of the process 200 enables the printer 100 to form chemical delivery devices
with varying distributions of one or more active chemicals.
[0050] Referring again to FIG. 2, the process 200 continues as the printer operates at least
one ejector to eject a predetermined amount of the active chemical into each cavity
in the portion of cavities in the substrate that corresponds to one of the activated
pixels with reference to the halftoned image data (block 216). Using the printer 100
as an example, the controller 128 operates the ejectors in the printhead array 104A
- 104C to fill each cavity in a first portion of cavities that corresponds to the
locations of the activated pixels for the first active chemical in the halftoned image
data. The ejectors in the printheads 104A - 104C eject a predetermined amount of the
chemical carrier and the first active chemical into each cavity that corresponds to
an activated pixel in the image data to ensure that each region of the chemical delivery
device has a concentration of the active chemical that corresponds to the concentration
parameter. In the printer 100, the controller 128 operates the ejectors in the printheads
108A - 108C to eject the predetermined amount of the chemical carrier including the
second active chemical into the second portion of cavities that correspond to the
activated pixels for the second active chemical in a similar manner to the operation
of the printheads 104A - 104C. Using FIG. 3A and FIG. 5 as examples, each of the activated
pixels in the image data that the controller 128 generates using the halftone screen
500 aligns with one cavity in the exposed layer of cavities in one region, such as
the region 304, of the chemical delivery device 300. The ejectors in the printheads
104A - 104C and 108A - 108C eject a predetermined amount of the chemical carrier and
active chemicals into the cavities that correspond to the first and second active
chemicals, respectively, to form each region of the layer in the chemical delivery
device 300 with the appropriate concentrations of the active chemicals.
[0051] Process 200 continues as described above for any additional layers in the chemical
delivery device (block 220). The printer 100 applies additional layers of the excipient
material to seal the exposed cavities in the chemical delivery device and encapsulate
the active chemicals in any cavities that received the active chemicals, and forms
another layer of cavities from the excipient material based on the chemical delivery
device structural data 138 to form another layer of cavities in the chemical delivery
device (block 224). In the illustrative embodiment of FIG. 2, the controller 128 repeats
the processing described in conjunction with blocks 208 - 216 for an embodiment of
the process 200 that generates the activated pixels in the halftoned image data for
each layer of the chemical delivery device individually. In another configuration,
the process 200 repeats block 216 using previously generated halftone data, such as
another two-dimensional arrangement of the halftoned data in a larger set of three-dimensional
halftoned data, to control the ejection of the active chemicals into the cavities
of the next layer of the chemical delivery device. Process 200 concludes when no additional
layers of cavities in the chemical delivery device remain (block 220) and the printer
100 seals the final layer of cavities with the excipient material (block 228).
[0052] The printer 100 and process 200 enable additive manufacturing production of chemical
delivery devices that release one or more active chemicals at varying rates and that
incorporate multiple types of active chemical material with chemical isolation between
the active chemicals until the chemical delivery device dissolves. The systems and
methods described herein enable production of chemical delivery devices with different
shapes and sizes with minimal reconfiguration of the three-dimensional object printer
100. Additionally, the printer 100 can produce chemical delivery devices with different
operating characteristics merely by using a different set of concentration parameters
to adjust the distribution of active chemicals throughout the structure of the chemical
delivery device, or by using an alternate halftone screen.
[0053] It will be appreciated that variants of the above-disclosed and other features and
functions, or alternatives thereof, may be desirably combined into many other different
systems, applications or methods. Various presently unforeseen or unanticipated alternatives,
modifications, variations or improvements may be subsequently made by those skilled
in the art that are also intended to be encompassed by the following claims.
1. A method of producing a chemical delivery device with a three-dimensional object printer
comprising:
receiving with a controller a first concentration parameter for a first active chemical
in a first region of a substrate in the chemical delivery device;
generating with the controller halftoned image data using a stochastic halftone screen
and with reference to the first concentration parameter, the halftoned image data
including a plurality of activated pixels that correspond only to locations of a first
portion of a plurality of cavities formed in a substrate that receive the first active
chemical; and
ejecting with at least a first ejector a predetermined amount of a first chemical
carrier including the first active chemical into each cavity in the first portion
of the cavities in the substrate with reference to the halftoned image data to produce
the chemical delivery device with a concentration of the first active chemical corresponding
to the first concentration parameter.
2. The method of claim 1 further comprising:
prior to ejecting the predetermined volume of the first chemical carrier including
the first active chemical, forming, with a dispenser, the substrate from a plurality
of layers including an excipient material.
3. The method of claim 2, the forming of the substrate further comprising:
applying with a spreader a powdered excipient material; and
operating at least a second ejector to eject a liquid binder in a predetermined pattern
to bind portions of the excipient material to form the substrate.
4. The method of claim 2, the forming of the substrate further comprising:
operating at least a second ejector to eject liquid drops of the excipient material
in a predetermined pattern to form the substrate.
5. The method of claim 1 further comprising:
receiving with the controller a plurality of concentration parameters of the first
active chemical for a plurality of regions of the chemical delivery device;
generating with the controller the halftoned image data using the stochastic halftone
screen with reference to the plurality of concentration parameters; and
ejecting with the at least first ejector the predetermined amount of the first chemical
carrier including the first active chemical into the first portion of the cavities
in the substrate with a concentration gradient through the plurality of regions of
the chemical delivery device corresponding to the plurality of concentration parameters.
6. A three-dimensional object printer comprising:
a support member;
at least a first ejector configured to eject a first chemical carrier including a
first active chemical toward the support member; and
a controller operatively connected to the at least first ejector and a memory, the
controller being configured to:
receive a first concentration parameter for a first active chemical in a first region
of a substrate in a chemical delivery device positioned on the support member;
generate halftoned image data using a stochastic halftone screen stored in the memory
and with reference to the first concentration parameter, the halftoned image data
including a plurality of activated pixels that correspond only to locations of a first
portion of a plurality of cavities formed in a substrate that receive the first active
chemical; and
operate the at least first ejector to eject a predetermined amount of a first chemical
carrier including the first active chemical into each cavity in the first portion
of the cavities in the substrate with reference to the halftoned image data to produce
the chemical delivery device with a concentration of the first active chemical corresponding
to the first concentration parameter.
7. The printer of claim 6 further comprising:
a dispenser configured to emit an excipient material to form the substrate of the
chemical delivery device; and
the controller being operatively connected to the dispenser and further configured
to:
operate the dispenser to form the substrate from a plurality of layers of the excipient
material on the support member prior to the ejection of the predetermined volume of
the first chemical carrier including the first active chemical.
8. The printer of claim 7 the dispenser further comprising:
a spreader configured to emit a powdered excipient material toward the support member;
and
at least a second ejector configured to eject a liquid binder in a predetermined pattern
to bind portions of the excipient material to form the substrate.
9. The printer of claim 6 the dispenser further comprising:
at least a second ejector configured to eject liquid drops of the excipient material
toward the support member in a predetermined pattern to form the substrate.
10. The printer of claim 6, the controller being further configured to:
receive a plurality of concentration parameters of the first active chemical for a
plurality of regions of the chemical delivery device;
generate the halftoned image data for the plurality of regions of the chemical delivery
device using the stochastic halftone screen stored in the memory with reference to
the plurality of concentration parameters; and
operate the at least first ejector to eject the predetermined amount of the first
chemical carrier including the first active chemical into the first portion of the
cavities in the substrate with a concentration gradient through the plurality of regions
of the chemical delivery device corresponding to the plurality of concentration parameters.